Production of high vacuum and high vacuum pumps



N. D. EMBREE 2,139,740

PRODUCTION OF HIGH VACUUM AND HIGH VACUUM PUMPS Dec. 13, 1938.

Filed June 24, 1937 Norris Dean Embree I N VEN T OR W.W BY Wyn/1W a/IW A TTORNEYS the same manner.

Patented Dec. 13, 1938 UNITED STATES PATENT OFFICE PRODUCTION or man vacuum, AND men vacuum PUMPS ware Application June 24, 1937, Serial No. 150,126

2 Claims.

This invention relates to the production of high vacuum and to improvements in high vacuum pumps.

In the co-pending application by K. C. D. Hickman #147,514 filed 6/10/37 there is described a new type of high vacuum pump operating upon the principle that surfaces are capable of sorbing gas molecules. A partial vacuum is produced by a backing pump of suitable type and further or complete evacuation is effected by sorption of the remaining gas upon a moving sorption surface. The sorbed gas is conveyed to a remote point of exhaust and discharged and the sorption surface again returned for removal of additional gas in The difliculties of prior known pumps are thus largely overcome. In order to move the sorption surfaces various expedients are disclosed among which is that requiring the rotation of a shaft extending through the pump wall. This necessitates a packed gland having a high degree of friction and since the Pump element could otherwise move freely, causes a much greater loss of energy than would be involved. if a packed gland were not used.

This invention has for its object to provide a high vacuum sorption pump which does not require transmission of force through ashaft extending through the wall of the pump. Another object is to provide a sorption pump in which the sorption surface is caused to move by radiation. A further object is to provide a sorption pump in which the sorption surfaceis caused to. move or rotate by radiation after the mannerof the Crookes radiometer. appear hereinafter.

These objects are accomplished by the herein described invention whichcomprlses absorbing or adsorbing gases from the chamber to be evacuated upon a. suitable sorption surface and causing the sorption surface to move to the high pressure or exhaust side of the pump by the impelling action of radiation.

In the following examples and description, I have set forth several of the preferred methods of carrying out my invention, but it is to be understood that they are given for the purposes of illustration and not as limitations thereof.

As set forth in the application above referred to, the sorption pump enables the emcient re- Other objects will moval of gas from the chamber to be evacuated,

. chamber, it is found that the proportion of gases sorbed on the walls is considerably greater than that existing in the space between the walls. As the gas in the space is removed gases are given up by the walls,'equilibrium being continuously established. It is desirable to remove gases from the walls if possible and therefore greatly increase the rate as well as the degree of evacuation. This situation, of course, is the reverse of that present at higher pressures where the amount of gas in the space is much greater than that sorbed on the walls of the chamber. By disposing the pump so that it forms at least a part of the wall of the chamber, the degree and rate of evacuation are greatly improved.

The pumps operating on the above principles can be constructed in a large variety of forms. They can take the form of a rotating drum or cylinder placed in a large conduit connected to the chamber to be evacuated, or they may be in the form of rotating vanes or bands, if desired. These various types of variations to which my invention can be applied are disclosed in detail in the co-pending Hickman application referred to. However, in order to: more clearly describe the principles of operation, I have illustrated in the accompanying drawing diagrammatic illustrations of two forms of apparatus in which my invention can be carried out. I

Referring to the drawing, Fig. l is a diagrammatic section of a sorption pump in which discharge of gases and rotation of the pump elements is simultaneously effected by radiation from a source outside the pump. Fig. 2 is a similar section of a pump embodying the principles of my invention, the discharge of gas and rotation of the pump element being effected by a sourceof radiation disposed inside the pump and adjacent to the rotating element.

In Fig. 1, reference numeral l designates an enlarged conduit connected to the chamber to be evacuated. Reference numeral 2 designates a conduit leading to the backing pump such as a High Vac oil pump. Reference numeral 3 designates a pump housing shaped in the form of a drum and connected on opposite sides to conduits l and 2. Reference numeral 4 designates a rotatable cylindrical sheet or drum which is mounted upon a shaft 5 whichis delicatelymounted upon bearings in the pump casing 3. Upon the surface of the drum 5 are mounted a plurality of vanes 6 in the manner shown. The vanes are of such proportions that they closely ap-- stantially the same.

a source of light and heat is so adjusted that= have a bright reflecting surface on the opposite side. A source of light, such as an electric light bulb, is designated by the numeral 1, and a focusing lens 8 acts to gather the light and focus it upon the black surface of the vanes 6 in the manner clearly shown in the drawing.

The construction of the pump illustrated in Fig, 2 is substantially the same as Fig. 1 except that a heated filament 9 is disposed inside the pump and is provided with. a reflector 10 which serves to throw the light and heat upon the black surface of the vanes 6 as shown.

In the operation of the pump illustrated in Fig. l, the vacuum pump connected to conduit 2 is put into operation to produce a relatively low pressure below .1 of a mm. and preferably below .01 mm. A source of radiation I and the lens 8 are so adjusted that the light and heat rays are focused upon the black surface of the vanes 6 and thereby cause the drum 4 to rotate. Gases sorbed on the surfaces of vanes 6 at the inlet l of the pump are conveyed by the rotation of the drum to the exit conduits of the pump 2 and are discharged by the heat focused on the sorption surface. The gases thus discharged are removed from the conduit 2 by the backingpump. Gases diffusing into the conduit I from the chamber to be evacuated, and those given up by the walls of the chamber and/or conduit are continuously sorbed on the surfaces of the vanes 6 and conveyed to the low vacuum side of the pump and discharged bythe backing pump in the manner described.

The operation of the pump of Fig. 2 is sub The filament 9 serving as the vanes are caused to rotate and suflicient heat is concentrated on the surface by the lens to remove sorbed gases. Gases thus removed are continuously evacuated by the vacuum pump connected to conduit 2.

It is apparent that many obvious-changes and variations can be made in the above described apparatus without departing from the scope of.

my invention. For instance, the number of vanes can be increased or decreased to suit the particular pumping problem involved. They need not be disposed on a cylindrical surface, but may be fastened to a rotating sheet or drum of any suitable shape, which is mounted with sufficient delicacy that it can be rotated by the source of light or other radiation on the principle of the Crookes radiometer. The vanes can be constructed of any suitable material having sorptive action. Metals or glass can be used and preferably are coated with materials increasing the reflecting and/or sorption power. Aluminum coated with a thin coating of aluminum oxide has been found to be an excellent material for construction of the sorption surfaces. Materials having a desirable adsorption or absorption action such as silica gel, activated carbon or zeolites can be used. Any substance having a lower vapor pressure than the vacuum to be produced and having the property of absorbing or adsorbing gases is contemplated as being within the scope of my invention. The blackening of the surface of the rotating vanes can be accomplished in any suitable manner using carbon dyes, varnishes, paints or any other desirable material. It is to be understood that radiation in general such as light, infra red, ultra violet, X-rays, Hertz waves, etc., may be employed as the impelling force.

The mode of operation of the sorption pumps especially as regards construction, method of discharging sorbed gases and pressure range against which they operate has been more fully described in the above referred to application in the name of K. C. D. Hickman.

What I claim is: p

1. High vacuum pumping apparatus comprising in combination a sorption surface, means for conveying gas from the chamber to be evacuated to the surface, means for-removing gas from the surface at a remote point and means impelled by radiation for moving the sorption surface from the point of gas intake to the point of g removal. v

2. Means for producing high vacua which comprises in combination a movable sorption surface, a conduit connecting one side of the sorption surface to the chamber to be evacuated, a conduit connecting the approximately opposite side of the surface to a backing pump, means for removing gases from the surface at the last mentioned conduit and means located on the sorption surface causing it to move from one conduit to another, under the impelling action of radiation.

NORRIS DEAN EMBREE. 

